There has been known a liquid crystal display device including a region for displaying images in a transmissive mode by using a backlight as a light source, and another region for displaying images in a reflective mode by using external light as a light source. Such a liquid crystal display device can concurrently use the backlight and the external light, and therefore can always keep excellent display quality in any places, regardless of whether the liquid crystal display device is used indoors or outdoors. In such a liquid crystal display device, display is largely influenced by a gamma characteristic. In order to set the gamma characteristics of a transmissive display and a reflective display appropriately, a lot of research has been made from various points of view.
Originally, the liquid crystal display device for displaying images in both the transmissive mode and the reflective mode has been arranged such that a liquid crystal layer does not differ in thickness in a transmissive display region and a reflective display region. However, with this arrangement, the gamma characteristics of the transmissive display and the reflective display are different from each other. In order to cause the gamma characteristics of the reflective display region and the transmissive display region to be identical with each other, the liquid crystal layer has been arranged such that a thickness of the liquid crystal layer in the reflective display region is approximately a half of that in the transmissive display region.
FIG. 5 is a cross-sectional view illustrating a liquid crystal element 101 disclosed in Patent Literature 1. The liquid crystal element 101 employs a vertical alignment mode, and displays images in the transmissive mode and the reflective mode. The liquid crystal element 101 has an arrangement in which a liquid crystal layer is provided between a substrate 103 and a color filter substrate 102.
The liquid crystal element 101 includes a transmissive section 117 and a reflective section 118. On a substrate 103 side, a storage capacitor wiring 112, a gate insulating film 113, a transmissive electrode 109, a protection insulating film 114, and a reflective electrode 111 are stacked in this order on the reflective section 118 of the substrate 108. Among these, the gate insulating film 113 and the transmissive electrode 109 extend to cover the transmissive section 117. The reflective electrode 111 is arranged such that a reflective electrode film 116 is stacked on a resin interlayer insulating film 115. A top surface of the reflective electrode 111 has many convexities 111a and concavities 111b, and a flat portion 123.
Further, the color filter substrate 102 is arranged such that a transmissive substrate 105, a colored layer 106, and a transmissive electrode layer 107 are stacked in this order. Furthermore, in the transmissive section 117, a rivet 110a is provided so as to stick out from the transmissive electrode layer 107 toward a liquid crystal layer, and, in the reflective section 118, a rivet 110b is provided so as to stick out from the transmissive electrode layer 107 toward the liquid crystal layer.
In this arrangement, a cell thickness T of the transmissive section 117, a cell thickness R of the reflective section 118, a height Ri of a rivet, a diameter of a rivet, a thickness h of a resin film of the reflective electrode 111, a concavity-convexity depth Δ, a concavity-convexity pitch p, a clearance c, and the like are determined as appropriate. Particularly, in order to cause optical characteristics of the transmissive section 117 and the reflective section 118 to be identical with each other, the cell thicknesses T and R are set to be “R/T=1/2”.
FIG. 6 shows gamma characteristics of the transmissive display and the reflective display in such an arrangement. Specifically, FIG. 6 shows an example where both the gamma characteristics of the transmissive display and the reflective display are set to be at “γ=2.2”.
Citation List
Patent Literature 1
Japanese Patent Application Publication, Tokukai, No. 2006-322958 A (Publication Date: Nov. 30, 2006)
Patent Literature 2
Japanese Patent Application Publication, Tokukai, No. 2006-285255 A (Publication Date: Oct. 19, 2006)
Patent Literature 3
Japanese Patent Application Publication, Tokukai, No. 2004-333879 A (Publication Date: Nov. 25, 2004)
Patent Literature 4
Japanese Patent Application Publication, Tokukai, No. 2004-4828 A (Publication Date: Jan. 8, 2004)
Patent Literature 5
Japanese Patent Application Publication, Tokukai, No. 2003-157052 A (Publication Date: May 30, 2003)